1. Field of the Invention
The present invention relates to generally to drip irrigation system water valves, and more particularly to a mechanical soil moisture sensing device and drip irrigation valve and/or emitter with a built-in valve assembly in which water flow is controlled by hydrophilic material that opens and closes a valve in response to the presence and the absence of water permitted to enter the valve assembly.
2. Background Discussion
Drip irrigation changed how farmers, horticulturalists, and agronomists, water plants. The spot watering provided by a drip system irrigates plants more precisely. Drip systems use timers to operate solenoid controlled valves to turn on sections of main feeder lines. Larger hoses feed smaller ones, which connect to soaker hoses, drippers, and sprayers. Employing drip systems saves water. However, drip systems do not take into account variations in soil moisture content from one area to another. Water retention in soil is determined by soil type, heat, shade, wind, humidity and plant growth. Nothing in currently existing drip systems is designed to change water flow from dripper to dripper in response to such changing conditions. Electronic soil moisture devices have been developed to control watering, but they are only used to control the delivery of water to large irrigation zones. To date, despite numerous attempts to make a mechanical device that automatically controls water delivery to particular plants or very small watering zones, none have made it to market.
Drip irrigation systems are renowned for their efficiency, delivering restricted volumes of water in a slow and sustained fashion and only to the soils immediately surrounding plant roots. The rate at which the water is delivered ensures significant horizontal migration of the water, as well as vertical percolation down deep, and thus a thorough soaking of the soils.
As with nearly all extensive irrigation systems, drip irrigation systems that cover multiple watering zones are frequently controlled by valves set on programmable electronic timers. Watering zones are generally defined both by the particular area covered by a related set of emitters, and plants in each zone preferably have similar needs for water and sunlight. When control within zones is required, emitters for individual plants can be selected according to their flow rate per hour. Most emitters that drip directly onto soil deliver between V2 to 2 gallons of water per hour, though greater and more restrictive flow rates are available. Thus, plants scheduled for watering in the same time frame and on identical water lines can receive vastly different amounts of water. These elements of control—control valves and emitter types—contribute significantly to the overall system efficiency of the system and dramatically reduce water waste.
However, as efficient as they may be, even drip irrigation systems can be wasteful or deficient. This is because there are numerous factors even within small watering zones that affect the watering needs of particular plants, and emitters on such general control systems are simply not sufficiently respond to the needs of a particular plant in a particular location under ever changeable conditions—changing sun affecting plant metabolism rates, changing precipitation that may change even the need to water, changing temperatures and changing winds that affect transpiration and evaporation rates, and so forth. These factors highlight the difficulty in defining watering zones and plant watering needs on a plant-by-plant or a very small sub-zone basis. Thus, there remains a need for a drip system emitter that responds to the needs of the particular plant or group plants to which it delivers water by automatically adjusting its flow rate in relation to the actual soil water content, which is, in turn, based on all of the foregoing factors, plus some less changeable factors, such as soil drainage and saturation capacity.
There are presently no products in the market that solve these problems, most likely due only to the complexity of providing a successful and economically practicable product. Other devices employing expandable material (EM) as a valve on/off device have been proposed, but all fail in several important respects. Notably, devices leave the EM in contact with soil or via a conduit, and in such cases the EM becomes contaminated and ceases to work. In other cases the EM properties are never fully defined and may expand in nearly every direction such that they deform over time. Either the confined space in which they are placed does not accommodate such expansion or does not address how they will dry.
An EM needs air contact to dry, and to dry efficiently it must be small and expand only slightly with a small amount of water. To work properly, it must be rigid when fully expanded. Testing has shown that a 35% expansion from its size in a dry state is usually indicative of a material which offers the right characteristics to activate a valve and not deform over time. The prior art devices have failed to appreciate and to achieve these operating parameters.
Many devices are deployed in an “always on” EM device. Such devices cannot ever work properly for the present purposes. In such devices when the EM starts to dry, it causes the valve to leak well before the valve comes on, fully rewetting the EM and shutting the valve again before any appreciable amount of water is released. This problem causes plants to be under-watered and thus to render the device useless.
There must be a delay between the EM wetting and expansion during its wetting to keep the valve from shutting off prematurely and thus before full watering is achieved.
Further, the EM can never be in direct contact with the soil or via a conduit (like a wick) because micro pours in the EM will clog when contaminated preventing rewetting.
Accordingly, the EM must have only indirect contact with the soil, and this is a novel feature of the present invention. And it must have a direct relationship with the moisture content of the soil. If the EM closes the valve only at its fully expanded size, as it dries it will correspondingly open the valve too quickly, before the soil has dried sufficiently. This will cause a leak and throw off the reading, and it will cause overwatering.
Further, the EM must be quite small so that it can dry quickly and it must expand slowly enough that it does not shut off the valve during a watering cycle.
In the known art, most EM systems are simply too complicated and therefore commercially not viable. None take into account how an EM truly expands. Most fail to take into account how a valve will clog if exposed to air through calcification or material degradation. None have valves which function fully on or off. Variations in water flow will cause improper watering. Because they are not switches with simply on/off states, they need to expand into something that keeps the valve closed through a whole range of expansion distances.
Some published patents have attempted to address one or more of the problems set out above. None have led to the development of a viable product that works as needed. Exemplary patents include:
For instance, U.S. Pat. Appl. Pub. No. 2007/0277879 by Anderson, et al, teaches an irrigation control valve that uses a moisture sensitive element in contact with the soil and which expands or retracts depending on the moisture within adjacent soil. The moisture sensitive element is coupled to a moisture controlled member, and the moisture controlled member is moved further into the conduit with increasing moisture in the soil. The moisture controlled member and an electronically controlled member are located adjacent each other at the conduit. The electronically controlled member determines how far the moisture controlled member needs to move in order to fully block the flow of water in the conduit. An electronic controller is operable to determine the achieved level of moisture in the soil, by means of the electronically controlled actuator and the electronically controlled member.
U.S. Pat. No. 4,696,319, to Gant, discloses a moisture-actuated apparatus for controlling the flow of water by expanding when absorbing moisture from and contracting when emitting moisture into a moisture-conducting medium. Actuation is binary, with one state resulting from expansion of an actuating element when it absorbs moisture from a water-conducting medium; a second state results from the contraction of the actuating element when the element emits moisture into the medium. The actuating element includes a hydrophilic material disposed in a matrix of wicking material. In one embodiment the absorptive expansion is used to provide a high-moisture signal in the same embodiment, contraction of the element produces a low moisture signal for opening the valve. In other embodiments, the expansion and contraction of the actuating element is used to directly actuate a valve.
U.S. Pat. No. 5,113,888 to Beggs, describes a moisture sensitive irrigation valve interposed between a water source and a water outlet and which responds to changes in soil moisture. A diaphragm operatively connecting a water inlet and an outlet through a seal and reciprocates between open and closed positions. The diaphragm movement is restrained by pneumatic pressure opposing the water inlet pressure. In addition, a check valve is provided whereupon a moisture sensor disposed at a terminal portion of the device directly reading moisture level in the soil allows unidirectional air flow for self-purging of the sensor.
U.S. Pat. No. 5,148,825 to Gil et al teaches a moisture-responsive valve having a housing with an internal chamber, and water inlet and outlet openings. A valve assembly in the chamber includes a water-absorbing expansible body within the housing adjacent a moisture-permeable wall for controlling the movements of the valve member in response to the moisture passing through the moisture-permeable wall. The valve member is floatingly mounted between a first spring interposed between the valve member and the housing and urges the valve member away from the valve seat, and a second spring interposed between the valve member and the water-absorbing body and urges the valve member towards the valve seat.
U.S. Pat. Appl. Pub. No. 20040139650, by Haq, discloses an automatic watering system for that operates on moisture sensitive substance that deforms due to the absorption of moisture in the soil. In turn, it operates a valve through mechanical, electrical or chemical means. Valve operation selectively allows water to flow from a water chamber when the soil is dry. Water flow stops as the moisture content reaches a certain level in the soil.
None take into account freezing, which can damage all the devices.
The foregoing patents reflect the current state of the art of which the present inventors are aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicants' acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.